As to polymerization toners, a system using a styrene based resin as a binder resin has hitherto been the mainstream. But, from the viewpoints of low-temperature fixability, etc., in recent years, a chemical toner using a polyester based resin has been extensively and intensively investigated. However, in general, the polyester based resin is not obtainable through emulsion polymerization, and therefore, a polyester based emulsion has been obtained by phase conversion emulsification using an organic solvent or a method by a special emulsification-dispersion machine.
In general, in the chemical toner, after a manufacturing step of an atomized liquid, coagulation and fusion steps are carried out. However, there is involved a defect that the process is complicated because plural steps are undergone. For example, Japanese Patent No. 3351505 describes that an emulsion of a polyester based resin is obtained by introducing a molten resin into a high-speed rotation type continuous emulsification-dispersion machine. However, the apparatus is complicated, and there is risk that deterioration of the polyester resin occurs. Also, JP-A-2007-114665 describes the use of an organic solvent for dissolving a polyester therein. However, equipment for recovering the organic solvent is required, and a load to the environment is large. In addition, JP-A-2007-33769 involved problems that since a polycondensation reaction is carried out in water, not only a special technology is required, but it is difficult to increase the molecular weight. In addition, JP-A-2007-106906 describes that emulsification is carried out at a temperature of not higher than a softening point of the resin. However, there are involved problems that a dispersed particle does not become sufficiently small and that control of the particle size is difficult. In addition, JP-A-2007-187917 describes that a toner particle is formed without undergoing a coagulation step. However, there is involved a problem that control of the average particle size or particle size distribution is difficult.